Sp. Attack: 108
Sp. Defense: 70
Stat distribution-wise, Samurott's by far the best of the Gen V starters. While Emboar is an offensive powerhouse, its bulk leaves much to be desired, and Serperior may have better defenses, but even its HP is lackluster. Samurott, on the other hand, is the most balanced of the trio, and an excellent wallbreaker. Samurott can run defensive sets (Toxic Stall and such) as well as offensive ones, but his main role is that of a wallbreaker, being able to hit from the physical AND special sides. The most effective set for a wallbreaker Samurott consists of: Hydro Pump, Ice Beam, Aqua Tail and Dig for those annoying Electric-Types. Samurott's got just the moves and stats he needs to be an incredibly good Water-Type wallbreaker, even better than Poliwrath.
Samurott's a fearsome attacker, but it's also pretty decent on the defensive side, so it's kind of hard to counter him effectively without risking being KO'd by a STAB Hydro Pump coming off that 108 base Sp. Atk. but the best way to counter him is by far Pokémon such as Ampharos and Zekrom. Ampharos' massive Sp. Atk. hits Samurott's weak spot, and even if it survives a STAB Thunder/Thunderbolt, Ampharos' decent HP and Sp. Def. are enough to sponge a Hydro Pump and hit back for the kill. Zekrom does even better, resisting the Hydro Pump and firing off either a STAB Outrage or a Lightning Strike, both of which will probably 2HKO full HP Samurott.